The present invention relates to a device for projecting coating product, comprising at least one sprayer and a reservoir with piston.
It is known to use coating product sprayers borne on robots or automats, these sprayers being displaced opposite the objects to be coated. For certain applications, and particularly for hydrosoluble coating products, it is known, in particular from EP-A-0 274 322, to carry a reservoir of coating product at the end of the arm of a robot to supply one or more sprayers. When almost all the product contained in the reservoir has been consumed, it is necessary to clean this reservoir and to refill it.
The reservoir may include a piston whose displacement allows the coating product to be driven towards the sprayer.
The precision obtained for the flowrate of coating product during projection essentially depends on the precision of the displacement control of the piston inside the reservoir. Systems comprising a piston controlled by a rod are more precise than pneumatically or hydraulically controlled systems which necessarily comprise a pressure regulator constituting a dead volume which must be cleaned and leads to losses of coating product.
When the coating product contained in the reservoir has been used up, the piston is in the immediate proximity of the bottom of the reservoir since the main part of the product has been consumed. If the piston is applied against this bottom, to bleed the remaining coating product, the introduction of a cleaning product in the reservoir tangentially to the front face of the piston is no longer possible, with the result that this front face remains soiled by the coating product used previously. If the piston is not applied against the bottom of the reservoir in order to allow an eddying movement of the cleaning product, a corresponding volume of coating product is lost during each cleaning/filling operation, which increases the exploitation costs of the installation accordingly. In addition, part of the cleaning product is used only for evacuating this remaining coating product and not for effectively cleaning the front face of the piston, which corresponds to additional costs.
French Patent Application 2 722 432 discloses using a rod capable of being mechanically disconnected from the piston or from its means for driving in translation during cleaning or filling of the reservoir, which allows a movement of recoil of the front face of the piston during the introduction of a cleaning product under pressure. This solution is advantageous but requires elaborate drive means which include a position control system in order to allow a recoil, with a short but precisely controlled stroke, of these means with respect to the piston.
It is an object of the invention to propose an alternative solution to the problems set forth hereinabove, which does not require mechanical disconnection of the piston from its drive means.
To that end, the invention relates to a device for spraying coating product, comprising at least one sprayer and a piston reservoir, the displacement of the piston being controlled by an actuating rod, while the bottom of the reservoir is connected by at least one channel to a supply of cleaning product and/or of fresh product, characterized in that it comprises a module, elastically deformable in compression, incorporated in the kinematic linkage between the rod and the piston or between the rod and its drive means, this module allowing a movement of recoil of the piston during the introduction of the product in the reservoir from said channel and in the direction of the front face of the piston.
Thanks to the invention, a certain xe2x80x9celasticityxe2x80x9d is given to the positioning of the piston when it is in abutment against the bottom of the reservoir, this elasticity being able to be advantageously used for creating a space for circulation of cleaning product, of which the pressure of injection in the reservoir allows the deformable elastic module to be compressed. In other words, the piston is capable of a slight clearance which clears a space for circulation of the cleaning product. In addition, the device of the invention makes it possible to dampen a possible excess pressure while the reservoir is being filled with fresh cleaning product.
According to advantageous aspects of the invention, the device incorporates one or more of the following features:
The module is incorporated in an assembly intended to be disposed between one end of the rod and the rear face of the piston. In that case, this assembly advantageously comprises a first element for receiving the end of the rod and a second element adapted to cooperate with the rear face of the piston, the elastically deformable module being disposed between these first and second elements. These first and second elements may be provided to be connected by a mechanical linkage with clearance which may be formed by a rod provided with a head received with clearance in a housing of one of the elements mentioned above and fast with the other element.
The elastically deformable module is formed by a stack of Belleville washers. In that case, said washers may be provided to be arranged between the first and second elements mentioned above, around the said rod.
The elastically deformable module may also be formed by a block of material which is elastically deformable in compression, such as an elastomer. Other materials may, of course, be envisaged.
The constant of stiffness of the elastically deformable module is sufficient for it to be rigid during the spraying phases. This allows a precise control of the flowrate of product during spraying.